nit: `os.path` provides a helper function to split a file extension away from a path. The function you want is

http://docs.python.org/2/library/os.path.html#os.path.splitext

Please change the logic to check if it ends with the extension to use this function. It should look something like:

(Note: no guarantees on the one-liner tuple syntax)
```
return any(path.endswith(os.path.splitext(path)[1]) for x in self.extensions.split(' '))
```

Also, would you make the list comma-separated instead of space-separated? It's sort of a personal preference, but I feel that commas convey the concept of a list much better than spaces do.